/Engine/Plugins/Media/ElectraUtil/Source/ElectraHTTPStream/Public/ElectraHTTPStream.h
Returns the buffer holding the data to be POSTed to the server. Make sure to include a suitable "Content-Type: xxx" header viaAddHeader()
[IElectraHTTPStreamBuffer](API\Plugins\ElectraHTTPStream\IElectraHTTPStreamBuffer) & POSTDataBuffer()